The clinical and biological effects of the prenatal administration of fluorides in an effort to prevent dental caries in the offspring are not defined. Although numerous studies have explored maternal-fetal fluoride matabolism and the uptake of fluoride in fetal hard tissues, the data are of limited value because of analytical errors associated with the older fluoride assays used in such studies. Only two relevant studies have used currently accepted assays methods, and one of these reports plasma fluoride levels that are an order of magnitude higher than is reasonable. Furthermore, a practical, relevant and relatively inexpensive model animal system has not been identified on which appropriate controlled experiments can be conducted. We propose to use the guinea pig as a model system because: (a) tooth enamel forms prenatally; (b) the placenta is histologically similar to the human; (c) adequate fetal plasma, bone and enamel samples can be collected; (d) multiple fetuses allow for serial delivery and sampling; (e) guinea pigs are relatively inexpensive; and (f) we have conducted the necessary preliminary studies using the guinea pig. We have developed a modification of the micro-diffusion fluoride method which allows us to measure the apparently low fetal plasma fluoride levels (greater than .01 ppm) with accuracy. Such a method is crucial to the study of maternal-fetal plasma fluoride relationships. The project has two Specific Aims: (1) To determine the short-term effects of selected oral doses of fluoride on maternal and fetal plasma fluoride levels, and on fluoride uptake in fetal enamel in guinea pigs. And, (2) to determine the maternal and fetal plasma fluoride levels, and the fluoride concentrations in fetal enamel and bone in guinea pigs maintained on various fluoride regimens during gestation.